1. Field of the Invention
The present invention relates to solid-state relays. More specifically, the invention is a solid-state relay device and a method for its installation in a locomotive electrical cabinet.
2. Description of the Related Art
Solid-state relay technology has been present 15 years approximately in the general industry in association with alternating current sources or low control side voltages, and the technology has been employed in computerized trains for purposes such as microprocessing, but only in association with relatively low control side voltages. However, solid-state relays have not been used to handle the high control side voltages found in the main electrical cabinets of locomotives in which standard locomotive voltage, such as 74 volts on the load side and the control side, is the norm. Solid-state relays have traditionally been operable at 5 to 32 volts on the control side. The problem is that solid-state technology is lagging behind for applications involving standard locomotive voltages. A DC to DC power converter employed with the present invention is a key feature that enables the use of solid state technology in a locomotive electrical system at standard locomotive voltages. Typically, the properties inherent in AC better lend themselves to solid-state technology, because AC creates a less harsh electrical environment, i.e., it is not as demanding on the components. Thus, AC is favored within the solid-state industry as a whole. DC to DC power conversion had been performed in the solid-state industry, but not with high voltages such as those found in a locomotive.
Most all locomotives typically use mechanical relays to switch power to various loads. These mechanical relays are typically housed in a compartment in the main electrical cabinet of the locomotive. The problem with mechanical relays is that they are subject to failure through mechanical wear and tear. The switch contacts become worn, pitted, or develop a coating of carbon, leading to arcing and other transient problems. Solid-state relays offer certain advantages over mechanical relays, including faster switching times, greater reliability, and longer service life. However, the mechanical relays in older locomotives cannot be replaced directly by solid-state relays, since the mechanical relays were designed to operate on the locomotive's standard 74-volt DC electrical system, whereas solid-state relays require a power supply between 5–32 volts. Until the present invention, replacing mechanical relays with solid-state relays would require an external 5–32 volt power supply, which requires additional cost, and which requires additional space, as it could not fit in the existing main electrical cabinet. The present invention offers a solution by offering a retrofit solid-state relay assembly which uses DC-DC converters to operate from the locomotive's existing 74 volt electrical system, the assembly being configured to replace the mechanical relays in the main electrical cabinet.
The related art describes various components of an electrical circuit suitable for operating locomotive switches, but none discloses the present invention. The related art will be discussed in the perceived relevance to the present invention.
U.S. Pat. No. 5,537,285 issued to Robert J. Jenets et al. (Jenets hereinafter) on Jul. 16, 1996, describes a solid-state relay module suitable for accepting low-level digital signals from a digital computer, and for providing on/off control of heavy electrical loads. The relay and its methods are intended for electrically hostile environments, such that the relay may be exposed to spurious high voltages either on its input or on its load circuit. The relay and its methods are particularly intended for use in a locomotive throttle controller. The relay accepts low-level digital signals from a central processor computer in the throttle controller, and provides high power digital signals to the train lines that control the engine of the locomotive. The controlling signal for the Jenets' relay is a relatively low-voltage, low-power signal originating in a digital computer. Thus, the Jenets' device cannot be operated by standard locomotive voltages. Jenets' device is a transient voltage protection (snubber) circuit. It is essentially a solid-state relay device requiring a thyristor, but not a solid-state relay device in combination with a DC/DC power converter. Jenets' device is distinguishable for lacking the capability for operating on standard higher locomotive voltages.
U.S. Pat. No. 5,347,166 issued to Colin D. Schauder on Sep. 13, 1994, describes a valve for rapidly switching high voltage at high currents. The valve is distinguishable for its limited single operation.
U.S. Pat. No. 3,805,056 issued to Michael S. Birkin on Apr. 16, 1974, describes a vehicle control system for a vehicle moving along a track way. Birkin does not describe the present invention as claimed.
U.S. Pat. No. 5,016,840 issued to Angel P. Bezos on May 21, 1991, describes an end-of-train emergency arming apparatus and method for its use. Bezos does not describe the present invention as claimed.
U.S. Pat. No. 5,200,878 issued to Kiyoaki Sasagawa et al. on Apr. 6, 1993, describes a drive circuit for a current sense Insulated Gate Bipolar Transistor. Sasagawa et al. do not describe the present invention as claimed.
U.S. Pat. No. 5,222,492 issued to Carlton B. Morgan et al. on Jun. 29, 1993, describes a cardiac defibrillator including an electronic energy transfer circuit. Morgan et al. do not describe the present invention as claimed.
U.S. Pat. No. 5,594,287 issued to David B. Cameron on Jan. 14, 1997, describes a high voltage solid-state relay. Cameron does not describe the present invention as claimed.
U.S. Pat. No. 5,699,218 issued to Andrew S. Kadah on Dec. 16, 1997, describes a solid state/electromechanical hybrid relay device. Kadah does not describe the present invention as claimed.
European Patent Application No. 0 246 064 A2, published on Nov. 11, 1987, for Benjamin Pless et al. describes a two-channel defibrillator device. Pless et al. do not describe the present invention as claimed.
European Patent Application No. 0 326 290 A1, published on Aug. 2, 1989, for Paul E. de Coriolis et al. describes a method and apparatus for applying an asymmetric biphasic exponential waveform counter-shock to the heart. The publication does not describe the present invention as claimed.
European Patent Application No. 0 546 666 A2, published on Jun. 16, 1993, for Carlton B. Morgan et al. describes an electronic energy transfer circuit for delivering a cardiac defibrillation pulse to a patient. Morgan et al. do not describe the present invention as claimed.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.